Surfactants, such as alkyl benzenesulfonates or alkyl sulfates for example, are normally made up in solid form by spraying the raw materials in the form of aqueous solutions or pastes through nozzles into a tower, the droplets formed encountering hot air flowing in countercurrent. The fatty compounds crystallize during their free fall in countercurrent to the hot air and are normally continuously discharged as an end product from the conical lower part of the spray tower. The drying air charged with organic material is passed through cyclones to separate the fine particles entrained. A fan transports the main stream back into the spray tower in a circuit via the cooler. A part stream is generally passed via the waste air system to the boiler house while the fresh air stream required is taken in from the surrounding atmosphere.
Several one-component pressure nozzles, for example so-called solid-cone nozzles, are normally installed in the head of the spray towers. The product is sprayed through these nozzles into the spray tower. The jet issuing from the nozzle with high turbulence breaks up after only a short distance from the nozzle orifice and forms droplets, the break-up of the jet being additionally intensified by its spin. The powder produced in this way has a broad particle size distribution. On account of the fine dust accumulating and the danger of dust explosions, spray installations of the type in question are subject to the broader obligations of so-called malfunction operation which imposes stringent works safety requirements and adds to the cost of the production process.
Accordingly, there is a considerable demand among detergent manufacturers for a process which would allow the production of surfactant granules with a limited particle size distribution, more particularly with a negligible fine particle or dust component (<0.5 mm) of less than 1% by weight. At the same time, the surfactant granules would be distinguished by an improved dissolving rate.
Accordingly, the problem addressed by the invention was to provide a new process for the production of surfactant granules which would be free from the above-mentioned disadvantages.